One quick follow-up question and I'll end the hijack... Stock 1969 GTO nodular LS rear...
8.2 or 8.5?
Cone or clutch?

8.2 cone type. :)

Thanks Bart!

If your putting power to an 8.2 in an A body you probably should have something like a QA1 anti hop bar to make the rear end dig in and not have wheel hop. Wheel hop with a stock suspension A body seems to kill the 8.2 as much as anything. I don’t have a qA1 setup, we created ours, but my center control arms are raised up on the rear end like a QA 1 set up. It made a big difference, eliminated wheel hop completely using a 30” tall drag slick.

We put a Moser 12 bolt in my buddy’s 69 gto not to long ago. The rear came from JD we just ordered new backing plates with brakes and had him install them before he installed axles so we didn’t have to redo it. With brakes it was less that $3500.00. It is far better than any rebuilt stock 12 bolt you’re going to find. With that said take a better look at your 10 bolt it might be a nodular center section. The 10 we pulled from his car is a N center section with 3.55 gears. Now it sits on jackstands in the corner. The purestock car he races has a 8.2 with a good posi unit and aftermarket axles it’s been getting pounded on for 20+ years now still going strong I’m talking hundreds of track passes.

I got in touch with Jim at JD Race. Given my specs, he recommended a 12 bolt as it's a direct bolt in. He said I'd need a shorter driveshaft with the 8.5. Another difference - while the 8.5 has bolt in axles, it's 28 spline (like the 8.2). The 12 bolt is 30 spline. He recommended rear discs with the 12 bolt setup to act as c-clip eliminators.

You're lucky that he's right around the corner from you. The cost of shipping from OH to CA isn't cheap - about $425. Even still, it might come up less than a Moser which is pricing out around $4600 after tax and shipping ($450). If I wanted the rear powder coated it would push me close to $5k.

The 8.2 in my car is a Nodular housing with the 4 pinion carrier. I put new aftermarket axles in it when I had the carrier rebuilt, but I can't remember what brand they are. I'm less worried about the housing or axles and more concerned about the carrier or 55 year old gears giving up. When Jim rebuilt the carrier 10 years ago, he said to go easy on it.

I went ahead an ordered a T/A girdle for now while I make up my mind on a new setup.

Aren't 12 bolts still a C clip axle? Do the aftermarket units come with bolt in ends?

Ive never understood why anyone would pay Moser aftermarket prices for a 12 bolt, when a 9 inch is basically the same price.

If you are sourcing locally and trying to stay cheap then a C clip 8.5, 12 bolt or 8.8 make more sense.

Factory 12 bolts are c-clip. The aftermarket 12 bolts have the option of bolt in or c-clip.

I figured they had to be. But they flat out change the ends and use custom axles right? Not like one of the C clip eliminator kits?

There is an absolute 0% chance I would pay $2000+ dollars for a C clip axle.

And I say that as a guy who regularly defends 8.5s as a budget option.

With what those moser 12 bolts cost, I'd take a long hard look at a nicely built 9 inch from a place like quick performance.

curious question, hope not to move convo away from op, i was thinking eaton posi unit went up $250 since 2019, richmond gears, then new after market axles, moser i think ? my bop corp n differential with that plate on back would make it capable of handling 500-600 hp ?

am i out to lunch? wont be any sticky tire launches

For what you’re doing sounds like what you have is fine but I know upgrades are fun.

https://www.quickperformance.com/9-F...7_p_20385.html

All the bells and whistles, $2800 with 3.25 gears and true trac. This is what I did and it's awesome. I've also got a 3.89 detroit locker 3rd member, I can swap them for strip or street.

how long does it take to swap out the 3rd member?

Considering I'm heading above $4k for a 12 bolt, this makes a 9" setup much more compelling.

Takes me about 2-3 hours. Gotta get it on jackstands, pull the tires, axles, exhaust, driveshaft, drain diff oil, remove 3rd member bolts and those little copper washers, pry the 3rd member loose, wrestle it out, wrestle the other one back up on a jack, shove it in place. Installation is the reverse of removal....

It's not a cakewalk, but still easier than having the gears set up in a GM rear end.

Thanks!

To me, that 9 inch from Quick Performance looks like the way to go. I went this route:

https://www.strangeengineering.net/p...g-mounts.html/

Which is great, but a 3.54 gear is the tallest gear you can get, and you still need a full gear setup to swap ratios. With that 9 inch, you get a very strong rear, easy gear changes, and a wide range of available ratios.

When I put my S60 in I got 3.54 gears because I had a standard wide ratio muncie. Now I have an ultrawide muncie and first gear is almost 3:1. If I had a 9" I'd swap the 3rd member for a 3.08 ratio, but not available for a Dana 60.

I'd have to think that 12 bolt looked awfully pretty under my car to go that route instead of the 9 inch!!!

Eaton makes a 30 spline 8.5 carrier and anyone can make 30 spline 10 bolt axles. I have Dutchman in the 81 and Moser in the 78. Dutchman could make a longer brake pilot than Moser would to locate a rear disc and hubcentric wheels. Moser we had to tack and extension on.
Moser and most others weld on bolt in bearing retainers-I added them to a factory 12 bolt in the IA Camaro with a 33 spline spool as you can but them separate.
Strange has a "Street C Clip Eliminator that use the same taper bearings 3.150 OD they use on weld ons

How do you distinguish the quoted Cutlass 8.5 from a Chevy 8.2, do you have a rear cover or bolt to bolt dimension or some other distinguishing feature?

I would say if you can get good price on a 8.5 with bolt in axles up grade at least to good 28 splines or jump to a 30 spline carrier and axles and it will be as good as a 12 bolt for what you are doing.